Capsule Velocity in Pipelines

Abstract

Capsule velocity in hydraulic and pneumatic pipelines is analyzed in its equilibrium state based on a coaxial annular flow model. The capsule is cylindrical and is assumed to move coaxially, and Coulomb friction is considered when the capsule has wheels. Properties of carrier fluid are included in a nondimensional friction parameter which consists of kinematic viscosity of fluid, density ratio, Coulomb frictional coefficient, pipe diameter and gravity acceleration. Effects of length/diameter ratio, diameter ratio and friction parameter on the capsule velocity are calculated. The maximum capsule velocity is limited by the diameter ratio. Pressure and shear forces on the capsule and a pressure drop across the capsule are also discussed, and the possibility of drag reduction due to the capsule is suggested.